Cellulose acetate spinning solutions and process of spinning fine denier filaments



United States. Patent This invention concerns a new spinning solution and the process of spinning such solution into fine-denier filaments. More particularly, this invention concerns the incorporation of relatively smallarnounts of certain compounds into cellulose acetate spinning solutions whereby the viscosity of the cellulose acetate solution is increased in a manner that facilitates the spinning of fine denier filaments therefrom.

In the production of cellulose acetate yarn, cellulose acetate is dissolved in acetone or the like solvent. The spinning dope isput under pressure and forced through small holes ororifices in a spinneret. The fine strands of dope are continuously pulled from the spinneret through a spinning cabinet where the solvent is evaporated by means of hot air. The denier of the resultingfilaments can be defined by the factors of dope solids, draft, dope density, and orifice diameter asfollows:

Denier per filament K (dope percent solids) (orifice diameter) (dopedensity) spinning draft The spinning draft is defined as the linear speed of yarn take-up divided by the linear extrusion speed of the spinning solution at the orifice. In many instances spinning draft is limited to about 1.8. Excessive draft can result in many broken filaments and filaments with reduced physical properties.

The above relationship suggests-changing the orifice diameter as, a means of varying the denier of cellulose acetate filaments. However, when spinnerets with orifices with diameters less than about 0.035 mm. are-used, me-

chanical difficulties may arisein the spinning operation.

The acetate spinning dope does not flow through the smaller holes at an even rate and the holes tend to become clogged.

The denier of cellulose acetate filaments can also be varied by varying the solids content of the spinning dope. It is apparent that lowering the solids concentration of a dope will decrease the denier of the resulting filament, assuming the extrusion rate and the take-up rate are held constant. However, when the solids content of cellulose acetate is decreased, the dope viscosity also decreases. This produces difficulties in controlling the proper flow rate of the dope through the spinneret. Also, dopes with low viscosity may tend to stick to the metal spinneret and are, therefore, diflicult to pull into filaments. One method of eliminating this problem is to use a cellulose acetate with a higher intrinsic viscosity than is normally used for cellulose acetate yarn. The higher cost of producing a high intrinsic viscosity ester has tended to make this approach unattractive.

In recent years there has developed a market for fine denier filaments. One particular use therefore is the manufacture ofv tobacco smoke :filters from such fine denier cellulose acetate filaments. It is apparent, therefore, that the development of simple, less expensive procedure for making such cellulose acetate filaments represents a highly desirable result.

After extensive investigation wehave discovered a relatively simple way by which such fine denier filaments may redetermined at intervals.

due

be produced without involving the change of presently used spinning equipment or other material changes in existing processes for producing cellulose acetate filaments.

This invention has for one object to provide a cellulose acetate spinning solution of increased viscosity but with relatively low solids content. Still another object is to provide a way of improving cellulose acetate spinning solutions whereby they may be more readily spun into fine denier filaments. A particular object is to provide a cellulose acetate spinning solution which has a relatively small amount of certain titanium compounds therein. Still a further object is to provide a method for spinning cellulose acetate filaments of relatively small deniers such as deniers of the order of 0.2-2 denier per filament. Other objects will appear hereinafter.

In the broader aspects of our invention we have found that commercial yarn grade cellulose acetate spinning dope diluted with acetone or equivalent solvents to a low solids content (15-23%), which concentration is not normally suitable for spinning, can be made suitable for spinning by the addition of 0.02 to 1.5 (based on the cellulose acetate) of titanium chelate esters. The titanium compounds apparently partially affect the cellulose acetate in some manner which results in a large increase in the viscosity of the cellulose acetate spinning dope. The large increase in dope viscosity,- on addition of very small amounts of titanium chelates, was quite unexpected. We have found, for example, that if the concentration of the dope additive in a cellulose acetate-acetiine dope is only 0.20% based on the cellulose acetate, the viscosity of the dope immediately increases approximately three-fold.

Therefore, the present invention may be accomplished by adding 0.02 to 1.5% (based on the cellulose acetate) of avtitanium chelate to a low solids cellulose acetate spinning dope, then spinning the dope into fibers using conventional cellulose acetate. spinning equipment.

The titanium chelates useful in carrying out this invention are those chelates which are acetone soluble, are fairly resistant to hydrolysis (most cellulose acetate spinning dopes contain some water), and which react with the free hydroxyl groups of the cellulose acetate. lated with octylene glycol, ethyl acetoacetate, diacetone alcohol or acetyl acetone are illustrative of useful dope additives. v

The cellulose acetate which can be used in carrying out this invention comprises yarn grade acetone soluble cellulose acetate with an acetyl content of 37-42% and an intrinsic viscosity of 1.4 to 2.0. The cellulose acetate spinning dopes which can be used in carrying out this invention consist of 10 to 23% cellulose acetate, 76 to 89% acetone, 1 to 3% Water and 0.02to 1.5% (based on the cellulose acetate) of the titanium chelate.

A further understanding. of our invention will be apparent from the several examples which follow-for illustrating certain of our preferred embodiments.

EXAMPLE I A cellulose. acetatedope wasv prepared consisting, of 20% cellulose acetate and 80% acetone. The dope was divided into 1 kg. samples One sample was used as a control. Titanium additive compounds of the present invention were added to the othersamples. Each dope was then mixed 30 minutes. The viscosity ofthe dopes was measured with a Brookfield viscometer. The dopes were stored at room temperature and the viscosity was The results shown on Table I illustrate how titanium complexes affected the viscosities of these dopes. The data indicates that the titanium additive increases the viscosity of the cellulose acetate very rapidly. Following this initial increase of viscosity, no further change in the dope is apparent.

Titanium chein accordance with the present invention.

'9 J EXAMPLE II V A cellulose acetate spinning dope consisting of 20% cellulose acetate, 78% acetone and 2% water was divided into two portions. One portion was spun using a conventional cellulose acetate spinning cabinet. A spinneret with orifices with a 0.035 mm. diameter was used. The spinning draft was maintained at 1.6. The dope stuck to the face of the spinneret, stopping up the orifices. No filaments with satisfactory tensile properties were obtained.

To the second portion of the dope was added 0.75% (based on the cellulose acetate) octylene glycol titanate On mixing, the viscosity of the dope increased from 8,000 cps. to 28,400 cps. This dope was spun into fibers using a conventional cellulose acetate spinning cabinet. A spinneret with orifices with a 0.035 mm. diameter was used. The spinning draft was maintained at 1.6. The filaments were 1.0 denier. They had a tensile strength of 1.3 g. per denier and an elongation of 32%.

EXAMPLE III A cellulose acetate spinning dope consisting of 15% cellulose acetate, 83% acetone, 2% water had a viscosity of 3,000 cps. The dope could not be spun into filaments using conventional techniques. 0.40% of ethyl acetoacetate titanate was added to the dope. Theviseosity in- Table I Viscosit of Do es C s. Additive and Amount y p p (Based on the Cellulose Acetate) After 30 1 Day 7 Days 30 Days Min.

Control 8, 000 8, 100 7, 800 8, 300 0,5% Octylene glycol titanate. 15, 700 16, 100. 15, 900 16, 200 0.6% Octylene glycol titanate. 28, 400 28, 600 28, 500 28, 700 0.20% Ethyl acetoacetate titanate 23, 600 24, 000 23, 200 23, 500 0.40% Ethyl acetoacetate titanate 140, 000 139, 500 142, 100 141, 500 0.60% Ethyl acetoacetate titanate gel gel gel gel 0.50% Diacetone alcohol titanate 119, 700 119, 200. 120, 500 120, 300

' somewhat different from the preferred solutions described in the above examples.

EXAMPLE IV A cellulose acetate spinning dope consisting of 20% cellulose acetate, 77% acetone and 3% water had a viscosity of 8,000 cps. The dope could not be spun into filaments using conventional techniques. 0.20% (based on the cellulose acetate) ethyl acetoacetate was added to the dope. The viscosity increased to 21,100 cps. The dope was then spun into fibers using a conventional spinning cabinet. A spinneret with 0.035 mm. orifices and a spinning draft of 1.7 was used. The fibers were 0.9

denier. They had a tensile strength of 1.4 g. per denier and an elongation of 22%.

The ethyl acetoacetate titanate used in this example was prepared by mixing one mole of tetraisopropyl ti- 5 tanate with four moles of ethyl acetoacetate. Four moles of liberated isopropanol were then distilled from the ethyl acetoacetate titanate.

The next two examples will show that in the present invention it is not necessary to remove the liberated aliphatic alcohol from the titanium chelate reaction mixture, although there may be instances where this is done as indicated in the preceding example.

EXAMPLE V A cellulose acetate spinning dope consisting of cellulose acetate, 78% acetone and 2% water had a viscosity of 8,000 cps. 0.20% (based on the cellulose acetate) ethylacetoacetate was added to the dope. The viscosity increased to 21,900 cps. The dope was then 20 spun into fibers using a conventional spinningcabinet.

0.85 denier fibers with tensile strength of 1.3 g. per denier and 27% elongation were obtained.

The ethyl acetoacetate titanate used in this example was prepared by mixing one mole of tetraisopropyl titanate with two moles of ethyl acetoacetate. No alcohol was removed from the reaction mixture.

EXAMPLE VI A cellulose acetate spinning dope consisting of 17% cellulose acetate, 81% acetone and 2% water had a viscosity of 8,000 cps. 0.5% (based on the cellulose acetate) acetyl acetone titanate was added to the dope. The viscosity increased to 27,400 cps. The dope was then spun into fibers using a conventional spinning cabinet. 0.70 denier fibers with tensile strength 011.4 g. per denier and 24% elongation were obtained.

The acetyl acetone titanate used in this example was prepared by mixing one mole of tetrabutyl titanate with two moles of acetyl acetone. No alcohol was removed from the reaction mixture.

The titanium additive materials used in this invention in the relatively small amounts of 0.2.to 1.5% may in many instances be obtained commercially. In certain cases the compounds may be prepared by relatively simple esterification methods if it is desired to prepare such compounds rather thanpurchase them. For example, the octylene glycol titanate described above is a compound having the general formula:

0-Cs 1e on (341100 Z/ /I|\ A a Hill 'and O-CaHu OH HO s5 3 Ti HO l OH a io 7 Compounds such as those used herein may be prepared in several ways illustrated by the following:

' One mole of a titanium ester such as tetraisopropyl titanate or tetrabutyl titanate is mixed with 1, 2, 3 or 4 moles of the appropriate oxy-compound. The liberated alcohol can be removed from the reaction mixture, but

aosaess where x=0, 1, 2, or 3 and R represents an alkyl or aryl hydrocarbon such as the ethyl, propyl, isopropyl, butyl, 2- ethylhexyl or phenyl group. R represents an oxy-compound capable of chelating with titanium such as dihydroxy, diketo, hydroxy keto compounds, hydroxy carboxylic acids and their esters and keto carboxylic acids and their esters.

While we prefer to operate with acetone solutions of cellulose acetate, since as is well known acetone is the common readily available commercial solvent frequently used for dissolving cellulose acetate as illustrated above, our invention will function when other solvents are used for the cellulose acetate. Accordingly, our invention is not limited to the particular cellulose acetate acetone solutions described above.

Fine denier filaments produced in accordance with this invention have utility for various purposes such as in the production of cigarette filters. An illustration of a cigarette filter prepared from fine denier filaments produced by the present invention is as follows:

18,000 filaments of 0.8 denier per filament cellulose acetate yarn were pulled together to form a tow. This tow was then crimped to 20 crimps per inch. The crimped tow was spread out to a width of two feet and sprayed with glycerol triacetate plasticizer until its weight had increased by 12%. It Was then compacted again into the form of a cord and processed into filter rods on a standard cigarette filter rod making machine. The rods were cut into 15 mm. lengths and attached to a domestic brand of cigarettes. These cigarettes were smoked on an automatic standard cigarette smoking machine. The smoke was collected and analyzed for its nicotine and tar content.

Only one-half as much tars and nicotine were obtained as was obtained from the same brand of cigarettes without a filter.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be elfected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A spinning solution consisting essentially of cellulose acetate, solvent therefore and an amount of titanium chelate compound of 0.02 to 1.5 based on the weight of the cellulose acetate, said chelate compound having the properties of dissolving in said solvent, causing a substantial increase in the viscosity of the spinning solution, being fairly resistant to hydrolysis and falling under the empirical formula:

wherein x represents a figure from the group consisting of 0, 1, 2 and 3, R represents a group from the class consisting of ethyl, propyl, ispropyl, butyl, Z-ethylhexyl and phenyl and R represents an oXy-compound capable of chelating with titanium from the group consisting of dihydroxy, diketo, hydroxy keto, hydroxy carboxylic acids and their esters and keto carboxylic acids and their esters.

2. The method for producing an improved cellulose acetate spinning solution which comprises adding 002 to 1.5 based on the weight of the cellulose acetate, of a titanium material chelated with a material from the group consisting of octylene glycol, ethyl acetoacetate, diacetone alcohol and acetyl acetone, to a solution which contains as essential ingredients cellulose acetate and acetone.

3. The method of making fine denier filaments which comprises forming a spinning solution containing cellulose acetate 15-23%, 0.02 to 1.5% based on the cellulose acetate of a titanium chelate having the properties of dissolving in the spinning solution solvent, causing at least a threefold increase in viscosity of the spinning solution as well as being resistant to hydrolysis and wherein the titanium chelate consists of titanium chelated with a material from the group consisting of octylene glycol, ethyl acetoacetate, diacetone alcohol and acetyl acetone.

References Cited in the file of this patent UNITED STATES PATENTS 2,072,102 Dreyfus Mar. 2, 1937 2,680,108 Schmidt June 1, 1954 2,916,777 Crane et al. Dec. 15, 1959 FOREIGN PATENTS 734,113 England July 27, 1955 

1. A SPINNING SOLUTION CONSISTING ESSENTIALLY OF CELLULOSE ACETATE, SOLVENT THEREFROM AND AN AMOUNT OF TITANIUM CHELATE COMPOUND OF 0.02 TO 1.5% BASED ON THE WEIGHT OF THE CELLULOSE ACETATE, SAID CHELATE, COMPOUND HAVING THE PROPERTIES OF DISSLOVING IN SAID SOLVENT, CAUSING A SUBSTANTIAL INCREASE IN THE VISCOSITY OF THE SPINNING SOLUTION, BEING FAIRLY RESISTANT TO HYDROLYSIS AND FALLING UNDER THE EMPIRICAL FORMULA: 